/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.net;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.Level;
import org.apache.log4j.Layout;
import org.apache.log4j.xml.UnrecognizedElementHandler;
import org.apache.log4j.helpers.CyclicBuffer;
import org.apache.log4j.helpers.OptionConverter;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.spi.ErrorCode;
import org.apache.log4j.spi.TriggeringEventEvaluator;
import org.apache.log4j.spi.OptionHandler;
import org.w3c.dom.Element;

import java.util.Properties;
import java.util.Date;

import javax.mail.Session;
import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;
import javax.mail.Transport;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;
import javax.mail.Multipart;
import javax.mail.internet.MimeMultipart;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.AddressException;

/**
 * Send an e-mail when a specific logging event occurs, typically on errors or
 * fatal errors.
 * 
 * <p>
 * The number of logging events delivered in this e-mail depend on the value of
 * <b>BufferSize</b> option. The <code>SMTPAppender</code> keeps only the last
 * <code>BufferSize</code> logging events in its cyclic buffer. This keeps
 * memory requirements at a reasonable level while still delivering useful
 * application context.
 * 
 * By default, an email message will be sent when an ERROR or higher severity
 * message is appended. The triggering criteria can be modified by setting the
 * evaluatorClass property with the name of a class implementing
 * TriggeringEventEvaluator, setting the evaluator property with an instance of
 * TriggeringEventEvaluator or nesting a triggeringPolicy element where the
 * specified class implements TriggeringEventEvaluator.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @since 1.0
 */
public class SMTPAppender extends AppenderSkeleton
		implements
			UnrecognizedElementHandler {
	private String to;
	/**
	 * Comma separated list of cc recipients.
	 */
	private String cc;
	/**
	 * Comma separated list of bcc recipients.
	 */
	private String bcc;
	private String from;
	private String subject;
	private String smtpHost;
	private String smtpUsername;
	private String smtpPassword;
	private boolean smtpDebug = false;
	private int bufferSize = 512;
	private boolean locationInfo = false;

	protected CyclicBuffer cb = new CyclicBuffer(bufferSize);
	protected Message msg;

	protected TriggeringEventEvaluator evaluator;

	/**
	 * The default constructor will instantiate the appender with a
	 * {@link TriggeringEventEvaluator} that will trigger on events with level
	 * ERROR or higher.
	 */
	public SMTPAppender() {
		this(new DefaultEvaluator());
	}

	/**
	 * Use <code>evaluator</code> passed as parameter as the
	 * {@link TriggeringEventEvaluator} for this SMTPAppender.
	 */
	public SMTPAppender(TriggeringEventEvaluator evaluator) {
		this.evaluator = evaluator;
	}

	/**
	 * Activate the specified options, such as the smtp host, the recipient,
	 * from, etc.
	 */
	public void activateOptions() {
		Session session = createSession();
		msg = new MimeMessage(session);

		try {
			addressMessage(msg);
			if (subject != null) {
				msg.setSubject(subject);
			}
		} catch (MessagingException e) {
			LogLog.error("Could not activate SMTPAppender options.", e);
		}

		if (evaluator instanceof OptionHandler) {
			((OptionHandler) evaluator).activateOptions();
		}
	}

	/**
	 * Address message.
	 * 
	 * @param msg
	 *            message, may not be null.
	 * @throws MessagingException
	 *             thrown if error addressing message.
	 */
	protected void addressMessage(final Message msg) throws MessagingException {
		if (from != null) {
			msg.setFrom(getAddress(from));
		} else {
			msg.setFrom();
		}

		if (to != null && to.length() > 0) {
			msg.setRecipients(Message.RecipientType.TO, parseAddress(to));
		}

		// Add CC receipients if defined.
		if (cc != null && cc.length() > 0) {
			msg.setRecipients(Message.RecipientType.CC, parseAddress(cc));
		}

		// Add BCC receipients if defined.
		if (bcc != null && bcc.length() > 0) {
			msg.setRecipients(Message.RecipientType.BCC, parseAddress(bcc));
		}
	}

	/**
	 * Create mail session.
	 * 
	 * @return mail session, may not be null.
	 */
	protected Session createSession() {
		Properties props = null;
		try {
			props = new Properties(System.getProperties());
		} catch (SecurityException ex) {
			props = new Properties();
		}
		if (smtpHost != null) {
			props.put("mail.smtp.host", smtpHost);
		}

		Authenticator auth = null;
		if (smtpPassword != null && smtpUsername != null) {
			props.put("mail.smtp.auth", "true");
			auth = new Authenticator() {
				protected PasswordAuthentication getPasswordAuthentication() {
					return new PasswordAuthentication(smtpUsername,
							smtpPassword);
				}
			};
		}
		Session session = Session.getInstance(props, auth);
		if (smtpDebug) {
			session.setDebug(smtpDebug);
		}
		return session;
	}

	/**
	 * Perform SMTPAppender specific appending actions, mainly adding the event
	 * to a cyclic buffer and checking if the event triggers an e-mail to be
	 * sent.
	 */
	public void append(LoggingEvent event) {

		if (!checkEntryConditions()) {
			return;
		}

		event.getThreadName();
		event.getNDC();
		event.getMDCCopy();
		if (locationInfo) {
			event.getLocationInformation();
		}
		cb.add(event);
		if (evaluator.isTriggeringEvent(event)) {
			sendBuffer();
		}
	}

	/**
	 * This method determines if there is a sense in attempting to append.
	 * 
	 * <p>
	 * It checks whether there is a set output target and also if there is a set
	 * layout. If these checks fail, then the boolean value <code>false</code>
	 * is returned.
	 */
	protected boolean checkEntryConditions() {
		if (this.msg == null) {
			errorHandler.error("Message object not configured.");
			return false;
		}

		if (this.evaluator == null) {
			errorHandler
					.error("No TriggeringEventEvaluator is set for appender ["
							+ name + "].");
			return false;
		}

		if (this.layout == null) {
			errorHandler.error("No layout set for appender named [" + name
					+ "].");
			return false;
		}
		return true;
	}

	synchronized public void close() {
		this.closed = true;
	}

	InternetAddress getAddress(String addressStr) {
		try {
			return new InternetAddress(addressStr);
		} catch (AddressException e) {
			errorHandler.error("Could not parse address [" + addressStr + "].",
					e, ErrorCode.ADDRESS_PARSE_FAILURE);
			return null;
		}
	}

	InternetAddress[] parseAddress(String addressStr) {
		try {
			return InternetAddress.parse(addressStr, true);
		} catch (AddressException e) {
			errorHandler.error("Could not parse address [" + addressStr + "].",
					e, ErrorCode.ADDRESS_PARSE_FAILURE);
			return null;
		}
	}

	/**
	 * Returns value of the <b>To</b> option.
	 */
	public String getTo() {
		return to;
	}

	/**
	 * The <code>SMTPAppender</code> requires a {@link org.apache.log4j.Layout
	 * layout}.
	 */
	public boolean requiresLayout() {
		return true;
	}

	/**
	 * Send the contents of the cyclic buffer as an e-mail message.
	 */
	protected void sendBuffer() {

		// Note: this code already owns the monitor for this
		// appender. This frees us from needing to synchronize on 'cb'.
		try {
			MimeBodyPart part = new MimeBodyPart();

			StringBuffer sbuf = new StringBuffer();
			String t = layout.getHeader();
			if (t != null)
				sbuf.append(t);
			int len = cb.length();
			for (int i = 0; i < len; i++) {
				// sbuf.append(MimeUtility.encodeText(layout.format(cb.get())));
				LoggingEvent event = cb.get();
				sbuf.append(layout.format(event));
				if (layout.ignoresThrowable()) {
					String[] s = event.getThrowableStrRep();
					if (s != null) {
						for (int j = 0; j < s.length; j++) {
							sbuf.append(s[j]);
							sbuf.append(Layout.LINE_SEP);
						}
					}
				}
			}
			t = layout.getFooter();
			if (t != null)
				sbuf.append(t);
			part.setContent(sbuf.toString(), layout.getContentType());

			Multipart mp = new MimeMultipart();
			mp.addBodyPart(part);
			msg.setContent(mp);

			msg.setSentDate(new Date());
			Transport.send(msg);
		} catch (Exception e) {
			LogLog.error("Error occured while sending e-mail notification.", e);
		}
	}

	/**
	 * Returns value of the <b>EvaluatorClass</b> option.
	 */
	public String getEvaluatorClass() {
		return evaluator == null ? null : evaluator.getClass().getName();
	}

	/**
	 * Returns value of the <b>From</b> option.
	 */
	public String getFrom() {
		return from;
	}

	/**
	 * Returns value of the <b>Subject</b> option.
	 */
	public String getSubject() {
		return subject;
	}

	/**
	 * The <b>From</b> option takes a string value which should be a e-mail
	 * address of the sender.
	 */
	public void setFrom(String from) {
		this.from = from;
	}

	/**
	 * The <b>Subject</b> option takes a string value which should be a the
	 * subject of the e-mail message.
	 */
	public void setSubject(String subject) {
		this.subject = subject;
	}

	/**
	 * The <b>BufferSize</b> option takes a positive integer representing the
	 * maximum number of logging events to collect in a cyclic buffer. When the
	 * <code>BufferSize</code> is reached, oldest events are deleted as new
	 * events are added to the buffer. By default the size of the cyclic buffer
	 * is 512 events.
	 */
	public void setBufferSize(int bufferSize) {
		this.bufferSize = bufferSize;
		cb.resize(bufferSize);
	}

	/**
	 * The <b>SMTPHost</b> option takes a string value which should be a the
	 * host name of the SMTP server that will send the e-mail message.
	 */
	public void setSMTPHost(String smtpHost) {
		this.smtpHost = smtpHost;
	}

	/**
	 * Returns value of the <b>SMTPHost</b> option.
	 */
	public String getSMTPHost() {
		return smtpHost;
	}

	/**
	 * The <b>To</b> option takes a string value which should be a comma
	 * separated list of e-mail address of the recipients.
	 */
	public void setTo(String to) {
		this.to = to;
	}

	/**
	 * Returns value of the <b>BufferSize</b> option.
	 */
	public int getBufferSize() {
		return bufferSize;
	}

	/**
	 * The <b>EvaluatorClass</b> option takes a string value representing the
	 * name of the class implementing the {@link TriggeringEventEvaluator}
	 * interface. A corresponding object will be instantiated and assigned as
	 * the triggering event evaluator for the SMTPAppender.
	 */
	public void setEvaluatorClass(String value) {
		evaluator = (TriggeringEventEvaluator) OptionConverter
				.instantiateByClassName(value, TriggeringEventEvaluator.class,
						evaluator);
	}

	/**
	 * The <b>LocationInfo</b> option takes a boolean value. By default, it is
	 * set to false which means there will be no effort to extract the location
	 * information related to the event. As a result, the layout that formats
	 * the events as they are sent out in an e-mail is likely to place the wrong
	 * location information (if present in the format).
	 * 
	 * <p>
	 * Location information extraction is comparatively very slow and should be
	 * avoided unless performance is not a concern.
	 */
	public void setLocationInfo(boolean locationInfo) {
		this.locationInfo = locationInfo;
	}

	/**
	 * Returns value of the <b>LocationInfo</b> option.
	 */
	public boolean getLocationInfo() {
		return locationInfo;
	}

	/**
	 * Set the cc recipient addresses.
	 * 
	 * @param addresses
	 *            recipient addresses as comma separated string, may be null.
	 */
	public void setCc(final String addresses) {
		this.cc = addresses;
	}

	/**
	 * Get the cc recipient addresses.
	 * 
	 * @return recipient addresses as comma separated string, may be null.
	 */
	public String getCc() {
		return cc;
	}

	/**
	 * Set the bcc recipient addresses.
	 * 
	 * @param addresses
	 *            recipient addresses as comma separated string, may be null.
	 */
	public void setBcc(final String addresses) {
		this.bcc = addresses;
	}

	/**
	 * Get the bcc recipient addresses.
	 * 
	 * @return recipient addresses as comma separated string, may be null.
	 */
	public String getBcc() {
		return bcc;
	}

	/**
	 * The <b>SmtpPassword</b> option takes a string value which should be the
	 * password required to authenticate against the mail server.
	 * 
	 * @param password
	 *            password, may be null.
	 */
	public void setSMTPPassword(final String password) {
		this.smtpPassword = password;
	}

	/**
	 * The <b>SmtpUsername</b> option takes a string value which should be the
	 * username required to authenticate against the mail server.
	 * 
	 * @param username
	 *            user name, may be null.
	 */
	public void setSMTPUsername(final String username) {
		this.smtpUsername = username;
	}

	/**
	 * Setting the <b>SmtpDebug</b> option to true will cause the mail session
	 * to log its server interaction to stdout. This can be useful when debuging
	 * the appender but should not be used during production because username
	 * and password information is included in the output.
	 * 
	 * @param debug
	 *            debug flag.
	 */
	public void setSMTPDebug(final boolean debug) {
		this.smtpDebug = debug;
	}

	/**
	 * Get SMTP password.
	 * 
	 * @return SMTP password, may be null.
	 */
	public String getSMTPPassword() {
		return smtpPassword;
	}

	/**
	 * Get SMTP user name.
	 * 
	 * @return SMTP user name, may be null.
	 */
	public String getSMTPUsername() {
		return smtpUsername;
	}

	/**
	 * Get SMTP debug.
	 * 
	 * @return SMTP debug flag.
	 */
	public boolean getSMTPDebug() {
		return smtpDebug;
	}

	/**
	 * Sets triggering evaluator.
	 * 
	 * @param trigger
	 *            triggering event evaluator.
	 * @since 1.2.15
	 */
	public final void setEvaluator(final TriggeringEventEvaluator trigger) {
		if (trigger == null) {
			throw new NullPointerException("trigger");
		}
		this.evaluator = trigger;
	}

	/**
	 * Get triggering evaluator.
	 * 
	 * @return triggering event evaluator.
	 * @since 1.2.15
	 */
	public final TriggeringEventEvaluator getEvaluator() {
		return evaluator;
	}

	/** {@inheritDoc} */
	public boolean parseUnrecognizedElement(final Element element,
			final Properties props) throws Exception {
		if ("triggeringPolicy".equals(element.getNodeName())) {
			Object triggerPolicy = org.apache.log4j.xml.DOMConfigurator
					.parseElement(element, props,
							TriggeringEventEvaluator.class);
			if (triggerPolicy instanceof TriggeringEventEvaluator) {
				setEvaluator((TriggeringEventEvaluator) triggerPolicy);
			}
			return true;
		}

		return false;
	}

}

class DefaultEvaluator implements TriggeringEventEvaluator {
	/**
	 * Is this <code>event</code> the e-mail triggering event?
	 * 
	 * <p>
	 * This method returns <code>true</code>, if the event level has ERROR level
	 * or higher. Otherwise it returns <code>false</code>.
	 */
	public boolean isTriggeringEvent(LoggingEvent event) {
		return event.getLevel().isGreaterOrEqual(Level.ERROR);
	}
}
